1. Field of the Invention
The present invention generally relates to eye examining apparatus and more paticularly to apparatus for measuring eye refractive power which is provided with an optical system for forming an image of an eye fixation mark to effectively relax the sight regulation power of an eye to be examined.
2. Description of the Prior Art
An eye refractometer is an apparatus for measuring the refractive power or astigmatism of a eye in a state in which the sight regulation power acting on the examined eye is loosened. However, in practice, it is very difficult to relax the sight regulation power in eyes being examined. In general, the sight regulation power of human eyes has a tendency to spontaenously act when the eye looks into such eye examining apparatus. To solve the problem, the conventional eye refractometer has employed means for moving the image of the eye fixation mark in a direction such that the sight regulation power is loosened in an instant after setting the image at a certain finite distance. This conventional method of relaxing the sight regulation power involves some drawbacks. At the moment of the fixation mark image being moved, the person to be tested can hardly judge whether the image has been moved toward or away from him. As a result, he fails to perceive the image. Since the eye refractive power is measured in such state of the eye, it is apparent that a large error of measurement may be caused unless his eye is perfectly free of the sight regulation power at this moment.